In an internal combustion engine, a cylinder head is typically used, in combination with a main body of the internal combustion engine, to close one end of the cylinders formed in the main body of the internal combustion engine. The cylinders, pistons reciprocating in the cylinders, and the cylinder head define a combustion chamber having a variable volume therebetween. A valve is arranged in the internal combustion engine, to provide one of a flow of air and a mixture of air and fuel into the combustion chamber. Typically a separate valve is arranged in the cylinder head to provide exhausting of exhaust gases from the combustion chamber.
In most internal combustion engines the valves may include poppet valves, which are used to control the inflow and outflow of gases into the combustion chamber. These poppet valves are typically activated by a camshaft, which is rotatably coupled by a drive element to a crankshaft of the internal combustion engine. The rotatable coupling of the crankshaft to the camshaft provides a constant ratio between the speed of rotation of the crankshaft and the speed of rotation of the camshaft. The activation of the individual valves is thus fixed to the rotation of the crankshaft. No independent control of the valves is possible even if it is desired to achieve improved engine performance and/or emission characteristics.
The poppet valves are typically spring biased to a closed position thereof. To open the valves, the camshaft has to first overcome the bias of the springs, which leads to large energy expenditure for opening of the valves.
An alternative cylinder head using spherical rotary intake and outlet valves accommodated therein is shown in U.S. Pat. No. 6,779,504, issued to Coates on Aug. 24, 2004. The Coates cylinder head is formed by two separate body portions. The body portions when assembled to each other define a plurality of spherical valve chambers. The valve chambers are each conformed to the shape of a single spherical valve to be accommodated therein. Each of the two body portions of the cylinder head has a plurality of cavities formed therein, which forms one half of the spherical valve chambers. Further, bearing cavities adjacent to the cavities forming the spherical valve chambers are provided in each body portion. When the body portions are assembled, these bearing cavities form a passage for accommodating bearings and a drive shaft for the rotary valves therein.
Flow of air between the cylinder head and the cylinder of the Coates patent is controlled by each of the spherical rotary valves accommodated in the cylinder head. In particular, flow of gases is allowed through an opening in the spherical surface of the rotary valve, which is brought into alignment with a flow opening in the lower body part of the cylinder head, and through the side surfaces of the spherical rotary valves. To provide a required air flow through the rotary valve, the rotary valve has to be of a certain size, and especially a certain height.
Flow of exhaust gases passing through the rotary valves of the Coates patent is directed from the sides of the rotary valves toward the bearings accommodated in the bearing passages, which may lead to overheating and thus malfunctioning of the rotary valves. Furthermore, during in-flow and out-flow of gases, turbulences are likely to occur within the respective valve chambers, which may limit the flow of gases therethrough.
The present application is directed to overcoming one or more of the problems set forth above.